Spark plug



June 6, 1944. s. M. DOBROSAVLJEVITCH 2,350,731

SPARK PLUG Filed June 25. 1940 BYz Patented June 6, 1944 SPARK PLUG Slobodan M. Dobrosavl slavia; vested in the 7 Claims.

This invention relates to spark plugs such as are used in connection with internal combustion engines, especially for acre-engines of high rating.

One object of the invention is to create a spark plug with a central electrode acting as aheat accumulator with efllcient heat exchange.

Another object of the invention is to improve the reliability of the spark plug to avoid dangerous deterioration of its elements by special shaping and arranging of these elements especially its central electrode and the insulation parts.

A further objector the invention is to provide a spark plug especially adapted for aero-engine with a solid and compact insulator such as of oxide of aluminum or steatite with perfect gastightness.

In the accompanying drawing an example of this invention is illustrated.

Fig. 1 represents a top plan view of the spark plug.

Fig. 2' represents the spark ring in a section on line 2-2 of Fig. 3.

Fig. 3 represents a side view of the spark plug.

Referring to Fig. 1 the numeral I represents the body of the spark plug having the usual screw 2 for the insertion into the engine cylinder head. I is the central electrode and II the outer electrode of the spark plug. A solid and compact insulator 3 of any suitable material is inserted in the body of the spark plug. The said insulator 3 is arranged in the body'l of the spark plug in such manner that free thermal dilatation of the insulator in the direction of its longitudinal axis is possible. The insulator 3 has in its interior a tapered surface 4 which serves as a seat for the central electrode l0. Above said seat 4 the insulator is provided with a chamber 5 of cylindrical form and below its seat with a second chamber 6 of cylindrical form.

jevitch, Belgrade, Yugo- Alien Property Custodian Application June 25, 1940, Serial No. 342,325 In Yugoslavia June 30, 1939 The central electrode 10 is made of metal.

It comprises a hollow main body having an enlarged head part l2 of an obtuse cone shape and adjacent it an end part I: of more acute cone shape. A part of the surface of the head part I2 is covered with a layer ll of conducting metal, such as copper. In the hollow space of the central electrode is arranged a core ii of material with good conductivity for heat such as copper. The core I! has an enlarged head part I6 preferably of globular shape and adjacent a tapered end part H.

In the cylindric chamber I of the insulator is arranged a spacing member 20, which by means of a nut 2| is pressed down against the head part l2 of the central electrode l0, thereby ilxing this electrode in central position in the body of the spark plug. The spacing member 20 is hollow and provided with a chamber 2 I Between the lower surface of th spacing member 20 and the upper surface of the head part I2 01 the central electrode I0 is arranged a washer 22 of heat resisting material. Parts of this washer 22 and of the spacing member 20 are covered with layers 24 of electric conducting material.

The electric cables and contacts necessary for the operation of the spark plug may be arranged in known manner in the chamber 2| of the spacing member 20 and other suitable elements of the spark plug.

The spark plug according to the inventiondiminishes the possibility of fouling and overheating and permits the use of compact insulators made of oxides of aluminum and steatite.

What I claim is:

1. A spark plug comprising a hollow central electrode filled in its interior with a highly ther mally conductive material, said electrode having a voluminous head-part and adjacent a tapered end-part, an insulator for said electrode having a seat for the head part of said electrode, and means pressing said head-part of the electrode against the seat of said insulator.

2. A spark plug comprising a hollow central electrode filled in its interior with a highly thermally conductive metal, said electrode having a voluminous head-part and adjacent a tapered end-part, an insulator for said electrode having a seat for the head-part of said electrode, and below said seat a chamber in the insulator through which the tapered end-part of the electrode passes without touching the walls of said chamber.

'3. A spark plug comprising a hollow central electrode filled in its interior with a highly thermally conductive metal, said electrode having a voluminous head-part and adjacent a tapered end-part, an insulator for said electrode having a seat for the head-part of said electrode and above said seat a chamber forming a part of said insulator through which said electrode with its voluminous head may be inserted to rest on said seat, and a second chamber forming a part of said insulator arranged below said seat,

through which the tapered end of said electrode passes without touching the walls of said chamber.

4. A spark plug comprising a hollow central electrode filled in its interior with a highly thermally conductive metal, said electrode having a voluminous head-part and adjacent a tapered end-part, an insulator for said electrode having in its interior a seat for the head-part of said electrode, a chamber of cylindrical form in said,

insulator arranged above said seat and a second chamber in said insulator arranged below said seat, said insulator being arranged in the body of the plug to provide free thermally dilatation in the direction of its longitudinal axis, and means arranged in the chamber above the seat of said electrode for pressing down the voluminous head seat for the head-part of said electrode, and

means to press said head 'of the electrode against the seat of said insulator.

6. A spark plug comprising a hollow central electrode filled with a highly thermally conductive metal, said electrode having a voluminous head-part and adjacent a tapered end-part, an insulator for said electrode having in its interior a seat for said head-part of the electrode, a chamber in said insulator arranged above said seat, a hollow spacing member of insulating inaterial arranged in said chamber, and means for pressing down said spacing member and thereby fixing the electrode in its central position.

'1. A spark plug comprising a hollow central electrode filled with a highly thermally conductive metal, said electrode having. a voluminous head-part of an obtuse cone-shape and adjacent an endpart of moreacute cone-shape, an insulator for said electrode having in its interior a seat for the head-part of said electrode, a chamber in said insulator arranged above said seat, a hollow spacing member of insulating material arranged in said chamber, and means for pressing down said spacing member and thereby fixing the electrode in its central position.

SLOBODAN M. DOBROSAVLJEVII'CH. 

